[The role of p38 mitogen activated protein kinase in the inflammatory response of human monocytes infected with nontypeable Haemophilus influenzae].
OBJECTIVE
To investigate the role of mitogen activated protein kinase (MAPK) pathway in the inflammatory response induced by nontypeable Haemophilus influenzae (NTHi).


METHODS
NTHi was a clinical isolate identified by serum agglutination test and 16S rRNA gene sequencing. The peripheral monocytes isolated from adult healthy donors were divided into medium-treated group, NTHi-stimulated group, SB203580 (p38 MAPK inhibitor) -pretreated group and UO126 (p44/42 MAPK inhibitor) -pretreated group. Monocytes were co-cultured with NTHi and harvested 1 h and 4 h after stimulation. The phosphorylation of p38 and p44/42 MAPKs was detected by Western blot. The expression of toll-like receptor 4 (TLR4) was examined by flow cytometry 16 h after bacterial stimulation. Monocytes were preincubated with SB203580 or UO126 for 1 h and then stimulated with NTHi for 4 h and 16 h, respectively. The level of TNF-alpha in the supernatants was determined by Enzyme-linked immunosorbent assay (ELISA).


RESULTS
The phosphorylation of p38 MAPK and p44/42 MAPK was rapidly induced by NTHi and continued for at least 4 h after stimulation. The expression of TLR4 on monocytes after NTHi stimulation was significantly up-regulated compared with the control group (11.8 +/- 1.6 vs 4.8 +/- 0.6, P < 0.05). The leve of TNF-alpha in the supernatants was increased 4 h and 16 h after bacterial stimulation compared with the control group (4 h : 16.4 +/- 5.3 vs 0.6 +/- 0.6, P < 0.01; 24 h : 30.2 +/- 10.7 vs 1.4 +/- 1.1, P < 0.01). SB203580 pretreatment decreased remarkably the TNF-alpha secretion from monocytes (P < 0.05) whereas UO126 had no significant effect on TNF-alpha level (P > 0.05).


CONCLUSIONS
TLR4 is probably involved in the inflammatory response of monocytes induced by NTHi whereas p38 MAPK is the key signal molecule in this inflammatory reaction.
Xu
Zhi-Hao
ZH
Department of Respiratory Medicine, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou 310009, China.
Xu
Feng
F
Shen
Hua-Hao
HH
Li
Lan-Juan
LJ
D002478:Cells, Cultured; D006192:Haemophilus Infections / Q000378:metabolism*; D006193:Haemophilus influenzae / Q000302:isolation & purification / Q000472:pathogenicity*; D006801:Humans; D007249:Inflammation; D009000:Monocytes / Q000378:metabolism* / Q000473:pathology; D051197:Toll-Like Receptor 4 / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; D014409:Tumor Necrosis Factor-alpha; D048051:p38 Mitogen-Activated Protein Kinases